The present invention relates to an electric box which may be used, for example, on an electric furnace. The electric box is provided with a disconnect feature, such that the box cannot be opened for inspection or service without disconnecting the electricity from the furnace coils and other controls housed within the box. However, after opening the box, a maintenance man may replace the plug for servicing.
In the present invention, an electrical forced-air furnace is provided with a recess in the furnace body forming the electric box. An electric disconnect block is mounted in the box, as are other furnace controls, fuses, wires, etc.
The electric box is formed partially, at least, by the sheet metal panels forming the walls of the furnace, and it is provided with a cover panel conforming to one of the side walls of the furnace and fully enclosing the electric box when assembled thereto. The cover panel may be hinged, if desired.
The electric disconnect block is provided with fuse holders through which incoming electrical power is routed, and a main disconnect switch. The disconnect switch includes sets of female connector terminals mounted in the block and electrically isolated from one another. One set of terminals is connected to the fuse holders from which power is fed to the furnace coils; and the other set is connected to a power input connector.
The main disconnect switch also includes a removable plug which, in the preferred embodiment, extends through an aperture in the cover panel of the electric box, when assembled, to establish electric continuity between the female connector portions of the disconnect switch. In this embodiment, the body of the disconnect plug includes side shoulder portions which extend beyond the cover panel aperture to form an interlock, whereby the cover panel of the electric box cannot be removed without first removing the disconnect plug, thereby shutting power off from the controls and the heater coils, prior to inspection or servicing.
In an alternate embodiment, the plug is received and held by a vertical support channel in the cover panel such that when the panel is opened, the plug is disconnected; and only then may the plug be removed from the support channel.
There is thus provided a safety disconnect for an electric furnace which prevents access into the electric box housing the electric controls and wires which de-energizes these controls and the heater elements before servicing or maintenance is performed. A seasoned maintenance man, on the other hand, will have had experience with such furnaces and realize that caution must be observed in servicing. Hence, the service man may take the disconnect plug from the cover panel after it is opened and insert it into the disconnect body, thereby reenergizing the controls for performing servicing or maintenance functions.
Other features and advantages will be apparent to persons skilled in the art from the following detailed description of a preferred embodiment accompanied by the attached drawing wherein identical reference numerals will refer to like parts in their various views.